1. Field
Exemplary embodiments of the present invention relate to a semiconductor design technology, and more particularly, to a semiconductor device which supports a refresh operation, and a method for driving the same.
2. Description of the Related Art
With the increase in integration degree of memories, intervals between word lines has been reduced. Reducing the intervals between word lines has caused an increase in the coupling effect between adjacent word lines.
Whenever data is inputted to or outputted from a memory cell, a word line is toggled between an active state and an inactive state. As the coupling effect between adjacent word lines increases, as described above, data of memory cells coupled to a word line adjacent to a word line which is frequently activated may be damaged. This phenomenon is referred to as word line disturbance. Word line disturbance may cause a problem in that the data of the memory cells are damaged before the memory cells are refreshed.
In order to solve this problem, a smart refresh technology has emerged. The smart refresh technology detects a target word line, which has been frequently activated, and refreshes memory cells coupled to word lines adjacent to the target word line. The smart refresh technology includes an additional refresh operation which is performed separately from a normal refresh operation (for example, auto-refresh operation).
FIG. 1 is a timing diagram illustrating an operation of a 1st conventional semiconductor device.
Referring to FIG. 1, two auto-refresh operations AR and two smart refresh operations SR+ and SR−1 are performed in response to a single external refresh signal EXT_REF. During a unit refresh period corresponding to the single external refresh signal EXT_REF, a plurality of banks BANK0/1, BANK2/3, BANK4/5, and BANK6/7 activate 1st to 8th word lines at the same time according to a 1st auto-refresh operation AR, activate an (N+1)th word line adjacent to an Nth word line according to a 1st smart refresh operation SR+1, activate an (N−1)th word line adjacent to the Nth word line according to a 2nd smart refresh operation SR−1, and finally activate 9th to 16th word lines at the same time according to a 2nd auto-refresh operation AR.
In other words, two auto-refresh operations AR and two smart refresh operations SR+1 and SR−1 during the unit refresh period per the external refresh signal EXT_REF are repetitively performed.
When the 1st semiconductor device is operated as described above, the following problems may occur. As the two auto-refresh operations AR and the two smart refresh operations SR+1 and SR−1 are repetitively performed, the 2nd auto-refresh operation AR at the previous unit refresh period and the 1st auto-refresh operation AR at the current unit refresh period are successively performed. The auto-refresh operation AR activates a larger number of word lines at the same time as the smart refresh operations SR+1 and SR−1. Thus, when the auto-refresh operations are successively performed, overcurrent occurs and current consumption inevitably increases.
FIG. 2 is a timing diagram illustrating an operation of a conventional 2nd semiconductor device.
Referring to FIG. 2, three auto-refresh operations AR and two smart refresh operations SR+1 and SR−1 are performed in response to a single external refresh signal EXT_REF. During a unit refresh period corresponding to the single external refresh signal EXT_REF, a plurality of banks BANK0/1, BANK2/3, BANK4/5, and BANK6/7 activate 1st to 8th word lines at the same time according to a 1st auto-refresh operation AR, activate an (N+1)th word line adjacent to an Nth word line according to a 1st smart refresh operation SR+1, activate an (N−1)th word line adjacent to the Nth word line according to a 2nd smart refresh operation SR−1, activate 9th to 16th word lines at the same time according to a 2nd auto-refresh operation AR, and finally activate 17th to 24th word lines at the same time according to a 3rd auto-refresh operation AR.
In other words, three auto-refresh operations AR and two smart refresh operations SR+1 and SR−1 during the unit refresh period per the external refresh signal EXT_REF are repetitively performed.
Even when the 2nd semiconductor device is operated as described above, the above-described problems may occur. Since the 2nd auto-refresh operation AR and the 3rd auto-refresh operation AR are successively performed at each unit refresh period, overcurrent occurs and current consumption inevitably increases.